Abstract

Feedback interferometers, in which the output fringe pattern is fed back to modulate the phase-difference in the interferometer via a spatial optical phase modulator, have been used for investigations of spatial structure formation¹, optical memories², and to achieve unambiguous fringe phase display for optical testing³. If these interferometers are operated in the negative feedback regime, it is possible to obtain output fringe patterns where intensity is almost linearly dependant on the physical path-difference in the system. This intensity distribution is fed back to a phase modulator in the interferometer as part of the negative feedback scheme, and so the resultant phase modulation partially cancels the interferometer path-difference - the degree of cancellation depending on the gain of the feedback loop. With an appropriate interferometer system (for example a radial shearing interferometer) it is, in principle, possible to automatically correct the aberrations of the input wavefront even at low optical powers⁴. We have built an interferometer of this type and describe its characteristics here.

© 1995 Optical Society of America